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Formula excellent when no scales available Print E-mail
Written by Larry Ellis, fishing columnist   
December 02, 2011 09:57 pm

Fred Anderson (left) hoists a fresh chrome-bright 25-pound Chinook he caught on Monday while back-trolling a sardine-wrapped banana plug. Jim Thom of Brookings and best friend, Bella joined in the photo. The Pilot/Larry Ellis
 

Fishing report for 

Nov. 25 - Dec. 1

No outdoor writer worth his salt feels threatened by getting a quote or from being quoted by a fellow colleague. It’s actually a very small world when it comes to the fishing and hunting biz, especially if you’ve been lucky enough to have been published in some of the more prestigious publications such as Northwest Sportsman, Salmon Trout Steelheader and Fishing & Hunting News.

At one time the latter publication, now out of business, had one of the best editors in existence at the helm, so whenever the opportunity arises to speak with Pat Hoglund, it is literally a columnist’s paradise.

 

 Since 2004, Pat has been editor and publisher of one of the classiest fishing magazines extant - Salmon & Steelhead Journal. In the spring 2006 issue, he wrote a treatise that has always been my go-to article when it comes to estimating the size of steelhead. It was entitled, “Cure for Big-Fish-Itis”, in which he states, “A strong and very persuasive argument can be made that a fisherman’s eyes are bigger than his scale.”  He then goes on to say “if you catch a steelhead that’s wild and must be released, the fish will get heavier as it swims away.”

Having been bit by the Big-Fish-Itis bug myself, all I can say is, “I can relate.”  In a town where most anglers don’t have access to a certified scale, Big-Fish-Itis has grown to an epidemic beyond dynamic proportions. Every fisherman’s door should be labeled, “Quarantined!”

Hoglund’s quest for the perfect steelhead weight estimating formula started when he caught a hatchery steelhead that was 35 inches long, 17 inches in girth and weighed nearly 15 pounds on a certified scale. After performing the standard fish weight estimating formula (length X girth X girth divided by 775), and coming up with 13.05 pounds, the 2-pound discrepancy warranted an immediate red flag.

Even if you used the formula stated in last week’s column for estimating a salmon’s weight (length X girth X girth divided by 800), the steelhead would have only weighed 12.64 pounds, almost 2 1/2 pounds lighter than the certified weight.

It stood to reason that if he were to catch a fish of a lifetime, particularly a wild steelhead that weighed in excess of 20 pounds and had to be released, he had to come up with a different fish weight estimating formula.

So Pat donned a white lab coat of his own and obtained 70 steelhead measurements from the I.G.F.A. (International Game Fish Association), data which included certified weights, lengths and girth measurements. He then contacted Lewis Lum, Professor of Mathematics at the University of Portland to seek out a possible cure for this common malady.

The result was the platinum-standard of steelhead weight estimating formulas, what is simply called “The Lum Formula”.

“I’ve gotten more notoriety from that than anything else I’ve done professionally,” Dr. Lum joked in a recent conversation I had with him last week.

Now that steelhead season is approaching, and there have been some dandies already landed, it would be a good idea to carry a calculator and a cloth measuring tape in case you want to obtain a fairly accurate weight before kissing your wild steelhead good-bye.

Measure the length of the fish in inches from the point of the nose to the center of the caudal (tail) fin. The girth is obtained around the circumference of the fish as measured directly ahead of the dorsal fin.

The Lum Formula multiplies the length (squared), multiplied by the girth, multiplied by .0007. In short, the weight equals the length times the length times the girth times .0007 (W = L X L X G X .0007). Remember that this weight-estimating formula is specific only for steelhead and should not be used for salmon.

“It only took between 1 to 2 hours,” noted Dr. Lum, a non-angler, when asked how long it took him to generate the formula. “That points out the power of mathematics if you know how to use it. You don’t have to know anything about fishing to be able to do some statistics.”

So if you’re wondering if your high school mathematics courses were all in vain, wonder no more. It might do a person good to take a refresher course.

“I had never really done any applied mathematics before this,” noted Dr. Lum, who was trained as a theoretical mathematician. “This was a real honest-to-goodness application, probably the first real application I’ve done in mathematics,” he laughed.

Just in case a person has caught a fish and weighed it, measured the length but had not taken its girth, a recent conversation with another local physicist who cut his teeth on advanced mathematics, Paul LeFebvre, worked out a formula for obtaining the girth.

According to Paul, it was a simple matter of algebra, who said the formula was: Girth = the weight of the fish divided by the length (squared), multiplied by .0007.

This was another perfect example of the ubiquitous use of mathematics in an applied setting. Last week, Wayne Sargent’s steelhead weighed exactly 15 pounds and had a length of 36 inches, but he had not attained a girth measurement.

In this case, the girth equaled 15 pounds divided by 36 X 36 (1296) multiplied by .0007 (.9072). 15 divided by .9072 resulted in a girth of 16.53 inches.

Remember, this is not advanced mathematics. All you need is a pocket calculator and substitute the numbers where they are supposed to go. While this may not be rocket science, it is a way of producing a life-like reproduction mount of your fish. Don’t forget to get several good photos so the taxidermist can do the art work.

Another great steelhead weight-estimating formula is the “length-minus-20” rule that is consistently within a pound’s weight in steelhead that are between 20- and 35- inches long.

So a steelhead that is 35-inches long should weigh approximately 15 pounds, give or take a pound.

Tight lines!

 

 

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